var clients = require('restify-clients');

async function callApi(val){
        const client = clients.createJsonClient({ url: apiUrl });
        await client.get('/my/url', (err, req, res, obj) => {
            if (err) {
                return err;
            } else {
                return obj;
            }
        });
}

var results = await callApi(val);

var results = callApi(val).then(data => {
                console.log(data);
            })